Method of making bearings



Dec. 12,' 1933. c. R. sHoRT Er AL METHODv OF MAKING BEARINGSl Filed May 3, 1929 Patented Dec. 12, 1933 UNITED STATES MEIHOD F MAKING BEARINGS charles n. snort -mi nonna P. noem-ing, Dayton, Ohio, assignors to The Moraine Prodlcts Company, Dayton, Ohio, a corporation of hio Application my 3, 1929. semi No. 360,074

1s claims. (cina-112) This invention relates to bearing elements havins a bearing-metal lining and a reinforcing backing of a different metal, especially bearing elements having a bearing lining of porous bronze 5 and a reinforcing backing of ferrous metal, particularly heat treated steel.

Reference is made to copending applications, Serial No. 188,929 filed May 5, 1927, Patent No. 1,768,528, and Serial No. 221,341 filed Sept. 22, 1927, Patent No. 1,834,746, by Charles R. Short, wherein there is disclosed methods of making bearing elements by forming a relatively thin sheet of porous metal and attaching it to a steel or other metal backing by an intervening tin or other metal bonding-coating applied either to the lining or backing vor both, all the metals being bonded or alloyed together by heat.

It has been found that in these bearings under severe use there is a tendency for the bearing lining to become loose due to a loosening of vthe tin bond from the backing, or due to the relatively low melting temperature of substantially pure tin, or one or more various other causes.

Now the present invention has for its object' the overcoming of such bonding difficulties between' bearing linings and their metal backings,

particularly to provide an improved method of securely and permanently bonding a bronze or other copper alloy part toa ferrous metal part, which bond will be very strong at a relatively high temperature.

In the methods described in the above men tionedicopending applications, whenever there is in the finished bearing a layer of free or unalloyed tin between the lining and backing, the maximum temperature at which such bearing can be run may be limited by the melting point of tin. The strength of the bond is of course greatly reduced as its temperature approaches the melting 40 point of tin.- Now the present invention provides a bond between the ferrous metal and the bronze by the use of tin, but in such manner that in the finished product the tin is so alloyed with copper that its melting point is raised above the maximum running temperature of the bearing which therefore may be above the melting point of tin. Briefly, .this object is accomplished by providing a very thin tin coating interposed be- I tween two metal surfaces both of which will alloy or diifuseinto the tin (such as copper or copper alloy), and heating for a sufiicient time and at a sufficient temperature to caus'e the entire thickness of tin to be alloyed with metal from adjacent metal surfaces. Since copper will readily diffuse into pure tin below 1000 F. it has been found that the pure tin layer can be converted into a copper-tin alloy without raising the temperature during this heattreatment beyond 1000 F., .or if need be, beyond 900 F. or lower. Hence this 80 invention is adapted to bond a bronze bearing lining directly to a heat treated steel part without raising the temperature of the heat treated steel part to a point where the temper of the steel will be impaired..

For the purpose of illustrating the method of y Fig. 1 represents a section through a heat treat-` ed steel connecting rod bearing assembled upon a bronze plug during the bonding step of the process, the thickness of the bonding layer, however, being greatly Vexaggerated for the sake of clearness.

Fig. 2 represents a microscopic view, magnified something like 125 times, of a section taken along line 2-2 of Fig. 1 prior to the heat treating or bonding step.

Fig. 3 is a view similar toA Fig. 2, but represents the section after the bonding step is comp eted.

In' the embodiment illustrated the semi-cylindrical porous bronze linings 10 are first made according to the above mentioned copending ap"A plications, or according to any other well known vand suitable. methods. The preliminary'forming of the linings 410 per se constitutes no part of this present invention and therefore need not be described in detail herein. The semi-cylindrical surfaces 12 of the heat treated steel connecting rod l1 and the cap `13 are preferably left rough or finely serrated by the tool marks when these surfaces are machined. These fine serrations may vary in width and depth considerably, but Figs. 2 and 3 illustrate the high ridges or 1ands'20 highly magnified from an actual distance apart of about 1/64 of an inch. The serrated steel surfaces 12 are first copper plated by any suitable known method, preferably to a `thickness of about .002 inch of Cu. In Fig'. 2

this Cu plating is designatedY by 21 and is represented as of substantially even thickness over the lands and grooves of the serrated steel surface. Next a very thin tin coating 22 'is applied to the copper plating 21 by any suitable means which will give a minimum thickness of tin coating. A suitable flux should be used before tinning, such as a water solution of zinc chloride which has been found satisfactory for this purpose. If the tinning vis done by dipping, all excess tin lshould be removed by some suitable method, such as by wiping off while hot with a rag or brush in a direction following the serrations. The tin coating 22 should completely instance as .0002 inch. It'hasbeen found that' the tin coating can be made extremely thin at 5 the high areas, that is,- on the summits of the lands 20, while in the grooves betweenthe lands it is somewhat thicker, as has been roughly illustrated in Fig. 2.

Now having thus prepared the steel surfaces 12 with Cu and tin coatings, the tin surfaces are again iluxed with a suitableflux as, for example, a water solution of zinc chloride, and the porous bronze linings assembled thereupon and the rod 11 and cap 13 then assembled upon a bronze plug l5 of the desired diameter by means of the bolts 16 and nuts 17 which should be drawn tight. There should be suilcientclearance between the meeting edges of the upper and lower steel parts as well as the linings 10 toA insure that the clampbearing surfaces of the linings. The bronze plug 15 having a. greater coefficient expansion than steel, assures that pressure will be applied to the joint to be bonded together all during the bonding heat treatment.

The bronze plug 15 should preferably be first coated with graphite and oil and baked to provide a coating thereon, or any other suitable method may be used which will prevent possibility of plug 15 sticking tothe porous bronze liningafter the bonding heat treatment, and

therefore permit ready disassembly of the parts. The assembly, shown in Fig. 1, is next heated to such a temperature and for such a time as will cause some of the copper of the copper plating 21 and some of the copper in the porous bronze lining 10` to alloy or diffuse into the tin layer 22 to such an extent that substantially all the tin becomes alloyed with copper and its melting point thereby materially raised, and in the meantime a strong bond is obtained between the copper plate 21 and the porous bronze 10 by this intervening layer of copper-tin alloy. The Cu plate 21 of course remains firmly bonded tothe steel on its opposite side and hence the entire seriesof layers is* bonded securely together.

It has been found by microscopic examination that the tin coating is thinnest -at the tops of the lands 20, and for this reason, presumably, the

' Cu entering the tin layer from both sides thereof converts the tin layer into a bronze of high copper content at these high areas 25 (designated in Fig. 3 bythe distance a-b). These bronze areas 25 are strong and tough and provide the main physical bond between the lining 10 and the steel.

In the grooves, or low areas 26 (designated in Fig. 3 by the distance from b to c) where the tin layer was thicker and where the clamping pressure between the layers is obviously smaller than at the lands 20, the diffusion of the copper through the tin layer is slower and the tin layer is apparently converted into the relatively hard and brittle CuaSn compound by the diffusion into the tin of copper from both sides thereof. Such CuaSn compound has a sumciently high melting point to withstand the highest desired running temperatures for bearings and also aids greatly in the thermal bond between the porous bronze 10 and the steel back for rapid conduction of heat away from the bearing material. It has been found, however,that the bond given by the tough bronze at the high areas 25 provides all the necesing pressure will be all taken directly upon the,

san/physical strengtnfana .the brittleness or the CuSn in the-low areas 26 is immaterial.

The above described bonding may be obtained 'by a heat treatment which will not impair the temper of the steel parts 11 and 13. The preferred method of such heat treatment at the present time comprises placing the assemblies shown in Fig. 1 in a closed container together with a iluxing material which volatilizes at or something below the desired bonding temperature and heating the container in a furnace for a period varying from 15 to 60 minutes at a maximum temperature wlch will not impair the temper of the steelparts, for instance, at 800 to`,900 F. This method of heating in a closed container within a iluxing atmosphere is more fully described and claimed in a copending application, Serial No. 333,014, filed Jan. 16, 1929, by Charles R. Short.

Of course, if desired, other suitable methods of heating to the desired temperature in a nonoxidizing atmosphere may be used, such for instance as dipping the assemblies of Fig. 1 in a molten lead bath maintained at the desired temperature. After removal from the lead bath, any lead which may adhere to the assembly can Abe easily removed with a wire brush while hot.

In such bonding heat treatments, at the higher temperatures a more complete diffusion of the Cu into the tin occurs, while at the lower temperatures greater amount of the brittle CuSn remains. However it has been found that the diffusion of the Cu into the tin can be increased with the length of time of heating, hence a longer period of heating at a lower temperature corresponds to a shorter period at a higher temperature. Therefore if there are no heattreated steel or other heat treated parts to protect from the higher temperatures, the bonding heat treatment of this invention may be carried out at temperatures much higher than 900 F., say up to 1400 F. and a saving of time of heating thus obtained.

The fundamental teachings of this invention are not limited to the use of bronze bearing linings, or a ferrous metal backing, or the use of any particular metals for forming the bonding alloy or alloys. For instance, instead of forming the bonding alloy from copper and tin, as described above, it may be formed from brass and tin, zinc and tin, cadmium and tin, copper and zinc, or other combinations of metals, by forming the metal coatings 21 and 22 accordingly. In each case there is formed a good bonding alloy intermediate the parts which 'are to be bonded to- 130 gether, having a higher melting point than that of its lowest melting component. If the bearing lining is of aluminum instead of bronze as described above, the coating 21 may be of copper with the coating 22 of zinc.

It is to be understood that this invention is not limited to the specific examples disclosed hereinabove for illustrative purposes, but only by what is claimed herebelow.

What is claimed is as follows:

1. The method of making a bearing element comprising: coating a ferrous metal backing with4 copper, pressing a bronze bearing lining against said copper coated backing with a thin layer of 145 tin between said vlining and copper, and heating the assembly below the melting point of copper for-such length of time as to cause the entire thickness of the tin layer to alloy with the cop- .per on each surface thereof, whereby the bronze 150 bronze.`

lining is firmly bonded to the ferrous metal backing.

2. The method of bonding a bronze structure to ferrous metal comprising: copper-plating the ferrous metal, pressing the bronze structure against the copper coated ferrous metal with a thin layer of tin therebetween, and heating the assembly below the melting point of copper for such length of time as to cause the entire thickness of the tin 'layer to alloy with both the copper plating and the bronze.

3. The method of bonding' a bronze structure to ferrous metal comprising: copper-plating the ferrous metal, pressing the bronze structure against the copper coated ferrous metal with a thin layer of bonding metal therebetween, and heating the assembly below the melting point of copper for such length of time as to cause the entire thickness of the layer of bonding metal to alloy with both the copper plating and the 4. The method of bonding a tin-alloying metal to ferrous metal comprising: copper-plating the -ferrous metal, pressing the tin alloying metal against the copper coated ferrous metal with a thin layer of 'tin therebetween, and heating the assembly below the melting point of copper for such length of time as to cause the entire thickness of the tin layer to alloy with both the copper plating and the tin-alloying metal.

5. The method of bonding a tin-alloying metal to ferrous metal comprising: copper-plating the ferrous metal, applying a thin coating of tin to the copper-plated surface, pressing the tin alloying metal against the copper and tin coated surface and heating the assembly below the melting point of copper for such time as to cause the entire thickness of the tin layer to alloy with the metal on each side thereof.

6. 'Ihe method of bonding a metal part to a second metal part comprising: pressing the two metal parts together, with a thin layer of bonding metal therebetween said kbonding metal being such that it will alloy with the surface of each of said metal parts under moderate pressure and temperatures, and then heating the parts while pressed together to such moderate temperature as will fuse said thin bonding layer and not fuse said two metal parts but for such length of time as to cause the entire thickness of the layer of bonding metal to alloy with the metal on each surface thereof.

'1. The method of bonding a ferrous metal part to a second metal part comprising: copper-plating the bonding surface of the ferrous metal part, pressing the two metal parts together with a thin layer of bonding metal there-between, said bondingimetal being such that it will alloy with both the copper coating and the second metal part, and then heating the parts While pressed together below the melting point of copper for such lengths of time as to cause the entire thickness of the layer of bonding metal to alloy with the two contacting metal surfaces.

8. The method of bonding a tempered steel part to a second metal part without adversely affecting the temper of the steel, comprising: copper-plating the bonding surface of the steel part, pressing the two metal parts together with a thin layer of bonding metal therebetween, said bonding metal being such that it will alloy with both the copper coating and with the second metal below 1100 part at moderate temperatures, and then heating the parts inl pressed together relation to such moderate temperatures as will not harm the temper of the steel but for such length of time as to cause 'the entire' thickness of the bonding metal to alloy with the two contacting metal surfaces.

9. The method of bonding a tempered steel part to a tin-alloying metal part comprising: v copper plating the bonding surface of the -steel part, pressing the two metal parts together with l a thin layer of tin therebetween, and then maintaining the parts while pressed together at such moderate temperature a's will fuse said thin layer of tin but not seriously harm the temper of the steel until the entire thickness of the tin layer is substantially all alloyed with the contacting metal of adjacent parts.

10. The method of bonding a ferrous metal part to a copper-containing part comprising: providing a finely serrated or roughened bonding surface on the ferrous metal, copper plating said roughened surface, tin coating over the copper leaving a very thin coat of tin on the high areas on said roughened surface, pressing the coppercontaining part against the tin coated surface and heating to such a temperature as will fuse only said tin coating until the entire thickness of the very thin tin coating on said high areas is substantially all alloyed with the copper metal on each side thereof.

11. The method of bonding a ferrous metal part to o copper alloy part comprising: providing a nely serrated or roughened bonding surface on the ferrous metal, copper plating said 110 roughened surface, tin coating over the copper leaving a very thin coat of tin on the high areas on said roughened surface. pressing the copper alloy part against the tin coated surface and heating in a fluxing atmosphere to only a moderate temperature until the entirethickness of the very thin tin coating on said high areas is substantially all alloyed with the metal on each side thereof.

12. The method of bonding a ferrous metal part to a copper alloy part comprising: providing a finely serrated or roughened bonding surface on the ferrous metal, copper plating said roughened surface, tin coating overl the copper leaving a very thin coat of tin on the high areas on Vsaid roughened surface. pressing the copper alloy part against the tin coated surface and heating in a fluxing atmosphere to a temperature F. until the entire thickness of the very thin tin coating on said high areas is alloyed '-30 with copper.

13. The method of bonding a heat-treated fer'- rous metal part to a copper alloy part comprising: providing a finely serrated or roughened bonding surface on the ferrous metal, copper plating said roughened surface, tin coating over the copper leaving a very thin coat of tin on the high areas on said roughened surface, pressing the copper alloy part against the tin coated surface and heating to a temperature which will not im- 1491 pair ythe prior heat treatment of said metal parts until the entire thickness of the very thin tin coating on said. high areas is substantially al1 alloyed with copper. 

